A class of machines exists in the art generally known as “scroll” machines for the displacement of various types of fluids. Such machines may be configured as an expander, a displacement engine, a pump, a compressor, etc., and the features of the present invention are applicable to any one of these machines. For purposes of illustration, however, the disclosed embodiments are in the form of a hermetic refrigerant compressor.
Generally speaking, a scroll machine comprises two spiral scroll wraps of similar configuration, each mounted on a separate end plate to define a scroll member. The two scroll members are interfitted together with one of the scroll wraps being rotationally displaced 180° from the other. The machine operates by orbiting one scroll member (the “orbiting scroll”) with respect to the other scroll member (the “fixed scroll” or “non-orbiting scroll”) to make moving line contacts between the flanks of the respective wraps, defining moving isolated crescent-shaped pockets of fluid. The spirals are commonly formed as involutes of a circle, and ideally there is no relative rotation between the scroll members during operation; i.e., the motion is purely curvilinear translation (i.e., no rotation of any line in the body). The fluid pockets carry the fluid to be handled from a first zone in the scroll machine where a fluid inlet is provided, to a second zone in the machine where a fluid outlet is provided. The volume of a sealed pocket changes as it moves from the first zone to the second zone. At any one instant in time there will be at least one pair of sealed pockets; and where there are several pairs of sealed pockets at one time, each pair will have different volumes. In a compressor, the second zone is at a higher pressure than the first zone and is physically located centrally in the machine, the first zone being located at the outer periphery of the machine.
Two types of contacts define the fluid pockets formed between the scroll members, axially extending tangential line contacts between the spiral faces or flanks of the wraps caused by radial forces (“flank sealing”), and area contacts caused by axial forces between the plane edge surfaces (the “tips”) of each wrap and the opposite end plate (“tip sealing”). For high efficiency, good sealing must be achieved for both types of contacts.
One of the difficult areas of design in a scroll-type machine concerns the technique used to achieve tip sealing under all operating conditions, and also at all speeds in a variable speed machine. Conventionally, this has been accomplished by (1) using extremely accurate and very expensive machining techniques, (2) providing the wrap tips with spiral tip seals, which, unfortunately, are hard to assemble and often unreliable, or (3) applying an axially restoring force by axial biasing the orbiting scroll or the non-orbiting scroll towards the opposing scroll using compressed working fluid.
The utilization of an axial restoring force first requires one of the two scroll members to be mounted for axial movement with respect to the other scroll member. When the compressor is designed as a high pressure compressor to compress a refrigerant like carbon dioxide, additional demand is placed on the axial biasing system as well as the other components of the scroll compressor.
In various embodiments, a compressor according to the present disclosure includes a shell assembly, a non-orbiting scroll member axially fixed relative to the shell assembly and including a first end plate, a first wrap extending from a first side of the first end plate, a discharge passage and an auxiliary passage. The first end plate and a shell assembly cooperate to define a chamber in fluid communication with the auxiliary passage. An orbiting scroll member includes a second end plate, a second wrap extending from the second end plate and meshingly engaged with the first wrap to form a suction pocket in fluid communication with a suction pressure region of the compressor, intermediate compression pockets, and a discharge pocket in fluid communication with the discharge passage. The auxiliary passage is in fluid communication with one of the intermediate compression pockets to provide pressurized fluid to the chamber to deflect the first end plate and the first wrap axially toward the orbiting scroll member.
In various embodiments, the chamber is isolated from the discharge passage. In various embodiments, the pressurized fluid within the chamber promotes engagement between the first wrap and the orbiting scroll member when the non-orbiting scroll member experiences thermal growth.
In various embodiments, the first wrap includes tips on a distal end and the pressurized fluid influences deflection of the non-orbiting scroll member to promote proximity of the tips to the second end plate.
In various embodiments, the discharge fitting is in fluid communication with the discharge passage in the non-orbiting scroll member and extending through the shell assembly to isolate the chamber from the discharge passage. The discharge fitting may extend into the discharge passage.
In various embodiments, the non-orbiting scroll member is axially fixed relative to the shell assembly at an outer perimeter region thereof. A bearing housing may be axially fixed relative to the shell assembly and fasteners may extend axially through the outer perimeter region of the non-orbiting scroll member and fixing the non-orbiting scroll member to the bearing housing.
In various embodiments, the orbiting scroll member is axially displaceable relative to the non-orbiting scroll member. A bearing housing may be axially fixed relative to the shell assembly and supporting the orbiting scroll member thereon. The second end plate and bearing housing may define a biasing chamber. The orbiting scroll member may include a biasing passage extending through the second end plate and in fluid communication with another one of the intermediate compression pockets to bias the orbiting scroll member axially toward the non-orbiting scroll member.
In various embodiments, a compressor according to the present disclosure includes a shell assembly, a non-orbiting scroll member including a first end plate axially fixed relative to the shell assembly and sealingly engaged with the shell assembly at an outer perimeter region thereof, a first wrap extending from a first side of the first end plate, a discharge passage and an auxiliary passage. A second side of the first end plate opposite the first side and the shell assembly cooperate to define a chamber in fluid communication with the auxiliary passage. The chamber may be defined from the discharge passage radially outward to the outer perimeter region. An orbiting scroll member includes a second end plate, a second wrap extending from the second end plate and meshingly engaged with the first wrap to form a suction pocket in fluid communication with a suction pressure region of the compressor, intermediate compression pockets, and a discharge pocket in fluid communication with the discharge passage. The auxiliary passage being in fluid communication with one of the intermediate compression pockets to provide pressurized fluid to the chamber to deflect the first end plate and the first wrap axially toward the orbiting scroll member.
In various embodiments, the chamber is isolated from the discharge passage. The second side of the first end plate may be isolated from the suction pressure region. The discharge passage may be located centrally in the non-orbiting scroll member.
In various embodiments, the first wrap includes tips on a distal end and the pressurized fluid influences deflection of the non-orbiting scroll member to promote proximity of the tips to the second end plate.
In various embodiments, a compressor according to the present disclosure includes a shell assembly, a non-orbiting scroll member axially fixed relative to the shell assembly and including a first end plate, a first wrap extending from a first side of the first end plate, a discharge passage and an auxiliary passage. The first end plate and the shell assembly cooperating to define a chamber in fluid communication with the auxiliary passage. An orbiting scroll member including a second end plate, a second wrap extending from the second end plate and meshingly engaged with the first wrap to form a suction pocket in fluid communication with a suction pressure region of the compressor, intermediate compression pockets, and a discharge pocket in fluid communication with the discharge passage. The auxiliary passage may be in fluid communication with one of the intermediate compression pockets to provide pressurized fluid to the chamber to deflect the first end plate and the first wrap axially toward the orbiting scroll member. A discharge fitting may extend into the discharge passage in the non-orbiting scroll member and extend through the shell assembly to isolate the chamber from the discharge passage.
In various embodiments, a compressor according to the present disclosure includes non-orbiting scroll member is axially fixed relative to the shell assembly at an outer perimeter region thereof. The non-orbiting scroll member includes a second side opposite the first side of the first end plate, wherein the second side is isolated from the suction pressure region. The discharge passage may be located centrally in the non-orbiting scroll member. The first wrap includes tips on a distal end and the pressurized fluid influences deflection of the non-orbiting scroll member to promote proximity of the tips to the second end plate.